linux-kernel - Re: shell outputs anything typed when the kernel thinks@...%

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Message-ID: <20080403231309.GB18242@tull.net>
Date:	Fri, 4 Apr 2008 10:13:09 +1100
From:	Nick Andrew <nick@...k-andrew.net>
To:	Madhou <madh2001@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: shell outputs anything typed when the kernel thinks@...%

On Fri, Mar 21, 2008 at 10:11:43PM +0100, Madhou wrote:
> When logging in a shell, one will type his username, 'return' and then his 
> password...

It sounds like you are describing behaviour of getty, not the
shell. That's because the tty device is set to echo typed characters at
the 'login:' prompt.  After getty receives your username either it or
/bin/login will turn off the echo flag and prompt for your password.

If it's a problem for you, patch getty to turn off echo (and cooked
mode) before the 'login:' prompt and perform all keyboard input
processing and echoing in the program.

> But just after 'return' the kernel is launched into thinking for long enough 
> to the point that users who do everything fast including logging in a shell 
> let the shell display the first letters of their passwords.
> This problem tends to be critical when the user makes a demonstration to a 
> bunch of people thanks to an overhead projector.

I don't think the kernel can be blamed for this behaviour, particularly
when your password is 'qwerty'. When demonstrating, setup a demo
username so you don't have to type your own password in front of a
roomful of people.

Nick.
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